Silicene layer-containing silicon substrate and method for producing same

Abstract

The present invention is a silicene layer-containing silicon substrate and a method for producing the same, the silicene layer-containing silicon substrate being characterized by comprising a silicene layer on a silicon substrate and a carbon-doped silicon layer on the silicene layer. Thus, provided are: a silicene layer-containing silicon substrate in which oxidation of the silicene layer is suppressed; and a method for producing the same.

Description

Silicon substrate containing a silicene layer and method for producing the same

[0001] The present invention relates to a silicon substrate containing a silicene layer and a method for making the same.

[0002] Two-dimensional materials have been attracting attention in recent years due to their high electron mobility and their potential as sensors. Graphene, which was isolated from graphite in 2004, is a prime example of this.

[0003] Silicon, which is also a group 14 element like carbon, can also adopt the same structure, and while carbon is graphene, the two-dimensional silicon material is known as silicene.

[0004] Silicene was first reported in 2011 and is known to be produced on the surface of silicon by growing Ag, diboron-zirconium, or iridium on the silicon and then heat-treating it at a high temperature (enough to sublimate the silicon). However, silicene is highly susceptible to oxidation and is difficult to handle.

[0005] Furthermore, germanene is known as a two-dimensional material made of germanium, a group 14 element. It has been pointed out that germanene is also susceptible to oxidation, and Patent Document 1 describes a method for preventing oxidation by using a cap layer. Graphene and hexagonal boron nitride are introduced as materials for this cap layer.

[0006] Japanese Patent Application Laid-Open No. 2022-124457

[0007] Although silicene, like graphene, is a material that has attracted much attention, it is still in the early stages of research, and improvements are needed, particularly in terms of its oxidation resistance, especially in the material of the cap layer.

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to provide a silicene layer-containing silicon substrate in which oxidation of the silicene layer is suppressed, and a method for manufacturing the same.

[0009] The present invention has been made to achieve the above object, and provides a silicene layer-containing silicon substrate having a silicene layer on a silicon substrate and a carbon-doped silicon layer on the silicene layer.

[0010] Such a silicene layer-containing silicon substrate has a silicon epitaxial layer doped with a high concentration of carbon as a cap layer on the silicene layer, thereby providing an excellent silicene layer-containing silicon substrate that can prevent oxidation of the silicene layer.

[0011] The present invention has also been made to achieve the above-mentioned object, and provides a method for producing a silicene layer-containing silicon substrate, including an Ag layer formation step of forming an Ag layer on a silicon substrate, a silicene layer formation step of annealing the silicon substrate to form a silicene layer on the Ag layer, and a carbon-doped silicon layer formation step of forming a carbon-doped silicon layer on the silicene layer.

[0012] According to this method for producing a silicene layer-containing silicon substrate, a silicon epitaxial layer doped with a high concentration of carbon is formed on the silicene layer as a cap layer, thereby making it possible to obtain a good silicene layer-containing silicon substrate that can prevent oxidation of the silicene layer.

[0013] In this case, in the Ag layer forming step, the Ag layer can be formed to a thickness of 0.3 nm or more by sputtering or vapor deposition.

[0014] This effectively prevents the silicene from having a non-uniform film structure, which would otherwise occur if heat treatment were performed in a state where silicon is partially exposed in the silicene layer formation step.

[0015] At this time, in the silicene layer forming step, the annealing can be performed in an atmosphere at a pressure of 133.3 Pa (1 torr) or less and a temperature of 1000° C. or more.

[0016] This allows silicon to sufficiently pass through (sublimate) the Ag film, and the silicene layer can be formed more reliably.

[0017] In this case, in the carbon-doped silicon layer forming step, epitaxial growth is performed at a growth temperature of 700 to 900° C. using a gas obtained by mixing trimethylsilane, monomethylsilane, or monosilane gas with a carbon source as a raw material, and the carbon concentration is 1×10 ２０ ~4 x 10 ２１ atoms / cm ３The carbon-doped silicon layer can be formed by:

[0018] This makes it possible to form a good carbon-doped silicon layer with reduced defects that can effectively prevent the diffusion of oxygen that oxidizes silicene.

[0019] As described above, the silicene layer-containing silicon substrate of the present invention has a silicon epitaxial layer doped with a high concentration of carbon as a cap layer on the silicene layer, thereby providing a good silicene layer-containing silicon substrate that can prevent oxidation of the silicene layer.Furthermore, the silicene layer-containing silicon substrate manufacturing method of the present invention makes it possible to obtain a good silicene layer-containing silicon substrate that can prevent oxidation of the silicene layer by forming a silicon epitaxial layer doped with a high concentration of carbon as a cap layer on the silicene layer.

[0020] 1A and 1B are schematic diagrams illustrating an example of a silicene layer-containing silicon substrate according to an embodiment of the present invention, and a process flow of a method for producing a silicene layer-containing silicon substrate according to an embodiment of the present invention.

[0021] The present invention will be described in detail below, but the present invention is not limited thereto.

[0022] As described above, there has been a demand for a good silicene layer-containing silicon substrate in which oxidation of the silicene layer is suppressed, and a method for producing the same.

[0023] As a result of extensive research into the above-mentioned problems, the inventors have discovered that a silicene layer-containing silicon substrate having a silicene layer on a silicon substrate and a carbon-doped silicon layer on the silicene layer, and having a silicon epitaxial layer doped with a high concentration of carbon as a cap layer on the silicene layer, can provide a good silicene layer-containing silicon substrate that can prevent oxidation of the silicene layer, and have completed the present invention.

[0024] The present inventors have also conducted extensive research into the above-mentioned problems, and as a result have discovered that a good silicene layer-containing silicon substrate capable of preventing oxidation of the silicene layer can be obtained by forming a silicon epitaxial layer doped with a high concentration of carbon as a cap layer on the silicene layer using a method for producing a silicene layer-containing silicon substrate including an Ag layer formation step of forming an Ag layer on a silicon substrate, a silicene layer formation step of annealing the silicon substrate to form a silicene layer on the Ag layer, and a carbon-doped silicon layer formation step of forming a carbon-doped silicon layer on the silicene layer, thereby completing the present invention.

[0025] [Silicen Layer-Containing Silicon Substrate] A silicene layer-containing silicon substrate according to the present invention will now be described with reference to Fig. 1. Fig. 1 is a schematic diagram of an example of a silicene layer-containing silicon substrate according to an embodiment of the present invention.

[0026] As shown in FIG. 1 , a silicene layer-containing silicon substrate 1 according to the present invention is a silicene layer-containing silicon substrate having a silicene layer 4 on a silicon substrate 2 and a carbon-doped silicon layer 5 on the silicene layer 4.

[0027] The silicene layer-containing silicon substrate 1 may include an Ag layer 3 between the silicon substrate 2 and the silicene layer 4 .

[0028] The silicon substrate 2 is not particularly limited, but may be a silicon single crystal substrate having a diameter of 100 mm or more, which may be manufactured using conventional single crystal manufacturing equipment and procedures.

[0029] The carbon concentration of the carbon-doped silicon layer 5 is 1×10 ２０ ~4 x 10 ２１ atoms / cm ３ The range is preferably 4×10 ２０ ~8 x 10 ２０ atoms / cm ３ This results in a good carbon-doped silicon layer in which defects are suppressed and which can effectively prevent the diffusion of oxygen that oxidizes silicene.

[0030] According to such a silicene layer-containing silicon substrate 1, by having a carbon-doped silicon layer 5, which is doped with carbon at a high concentration, on the silicene layer 4 as a cap layer, it is possible to prevent oxidation of the silicene layer 4.

[0031] [Method for Producing a Silicene Layer-Containing Silicon Substrate] Next, a method for producing a silicene layer-containing silicon substrate according to the present invention will be described. Figure 2 shows a schematic diagram of an example of a process flow for a method for producing a silicene layer-containing silicon substrate according to an embodiment of the present invention. As shown in Figure 2, the method for producing a silicene layer-containing silicon substrate 1 according to the present invention includes an Ag layer formation step (S1) of forming an Ag layer 3 on a silicon substrate 2, a silicene layer formation step (S2) of annealing the silicon substrate to form a silicene layer 4 on the Ag layer 3, and a carbon-doped silicon layer formation step (S3) of forming a carbon-doped silicon layer 5 on the silicene layer 4.

[0032] (Ag Layer Forming Step: S1) First, a thin film of Ag is formed on a silicon substrate 2, that is, an Ag layer 3 is formed. The Ag layer 3 can be formed by, for example, sputtering or vapor deposition.

[0033] In this case, the thickness of the Ag layer 3 can be set to 0.3 nm or more, i.e., a thickness of a monoatomic layer or more. If the thickness is 0.3 nm or more, a uniform silicene layer 4 can be formed over the entire surface of the silicon substrate 2 in the silicene layer formation step (S2).

[0034] Although there is no particular upper limit to the thickness of the Ag layer 3, it can be set to 5 nm. If the thickness is 5 nm or less, silicon can be efficiently diffused in the silicene layer formation step (S2), and the silicene layer 4 can be formed more reliably.

[0035] (Silicenes Layer Forming Step: S2) Next, the silicon substrate is annealed to form a silicene layer 4 on the Ag layer 3. By annealing, Si is sublimated, and the silicene layer 4 is formed on the Ag layer 3.

[0036] Annealing can be performed in a low pressure CVD apparatus, which allows sequential epitaxial processing within the same apparatus.

[0037] At this time, the annealing can be performed in an atmosphere at a pressure of 133.3 Pa (1 torr) or less and a temperature of 1000° C. or more.

[0038] If the pressure is 1 torr or less, silicon can sufficiently pass through (sublimate) the Ag film, and the silicene layer 4 can be more reliably formed. The lower limit is not particularly limited, but can be set to 0.1 torr. If the pressure is 0.1 torr or more, restrictions on the device caused by high vacuum, such as the ultimate vacuum capacity, can be effectively avoided.

[0039] The upper limit of the temperature is not particularly limited, but is preferably 1400° C. or less (the melting point of silicon or less). Taking into consideration wafer deformation and the heating mechanism of the apparatus, 1200° C. or less is more preferable.

[0040] (Carbon-doped silicon layer formation step: S3) Next, a carbon-doped silicon layer 5 is formed on the silicene layer 4. The carbon-doped silicon layer 5 can be formed by epitaxially growing the silicon layer 5 on a silicon substrate under reduced pressure in a reduced-pressure CVD apparatus using, as a raw material, a gas obtained by mixing a carbon source with, for example, trimethylsilane, monomethylsilane, or monosilane gas.

[0041] The growth temperature is preferably 700 to 900° C., and more preferably 730 to 750° C. This makes it possible to form an epitaxial layer with fewer defects.

[0042] The carbon concentration is 1 x 10 ２０ ~4 x 10 ２１ atoms / cm ３ The range is preferably 4×10 ２０ ~8 x 10 ２０ atoms / cm ３ This makes it possible to form a good carbon-doped silicon layer 5 in which defects are suppressed and which can effectively prevent the diffusion of oxygen that oxidizes silicene.

[0043] The growth temperature and carbon concentration can be adjusted in consideration of the thickness of the layer to be deposited.

[0044] The thickness of the carbon-doped silicon layer 5 is not particularly limited and can be adjusted in accordance with the thickness of the Ag layer and silicene layer to be laminated, but a thickness of 50 nm is sufficient as a guideline. In this way, a silicon substrate with a silicene layer sandwiched therebetween can be fabricated.

[0045] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0046] First, a single crystal silicon substrate having a diameter of 100 mm, a plane orientation of (100), boron doping, and a resistivity of 10 Ω·cm was prepared, and a Ag film having a thickness of 1 nm was formed on the silicon substrate by sputtering.

[0047] Next, this wafer was loaded into a reduced pressure CVD apparatus and annealed at 1170° C. for 70 minutes in a hydrogen atmosphere under a reduced pressure of 0.1 torr to form a silicene layer on the Ag layer.

[0048] Next, using trimethylsilane as the source gas, carbon was added at 1×10 ２０ atoms / cm ３ A 50 nm doped Si layer was grown to prepare a substrate with a silicene intermediate layer.

[0049] As a result, by forming a silicon epitaxial layer heavily doped with carbon as a cap layer on the silicene layer, it was possible to fabricate a silicon substrate having a silicene layer with suppressed oxidation.

[0050] This specification includes the following aspects. [1]: A silicene layer-containing silicon substrate having a silicene layer on a silicon substrate and a carbon-doped silicon layer on the silicene layer. [2]: A method for producing a silicene layer-containing silicon substrate, comprising: an Ag layer formation step of forming an Ag layer on a silicon substrate; a silicene layer formation step of annealing the silicon substrate to form a silicene layer on the Ag layer; and a carbon-doped silicon layer formation step of forming a carbon-doped silicon layer on the silicene layer. [3]: A method for producing a silicene layer-containing silicon substrate according to [2] above, comprising: forming the Ag layer to a thickness of 0.3 nm or more by sputtering or vapor deposition in the Ag layer formation step. [4]: ​​A method for producing a silicene layer-containing silicon substrate according to [2] above or [3] above, comprising: performing the annealing in the silicene layer formation step in an atmosphere at a pressure of 133.3 Pa (1 torr) or less and a temperature of 1000°C or higher. [5]: In the carbon-doped silicon layer forming step, epitaxial growth is performed at a growth temperature of 700 to 900°C using a gas obtained by mixing trimethylsilane, monomethylsilane, or monosilane gas with a carbon source as a raw material, and a carbon concentration of 1 x 10 ２０ ~4 x 10 ２１ atoms / cm ３ The method for producing a silicon substrate containing a silicene layer according to [2], [3] or [4] above, comprising forming the carbon-doped silicon layer.

[0051] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A silicene layer-containing silicon substrate, characterized by having a silicene layer on a silicon substrate and a carbon-doped silicon layer on the silicene layer.

2. A method for producing a silicene layer-containing silicon substrate, comprising: an Ag layer formation step of forming an Ag layer on a silicon substrate; a silicene layer formation step of annealing the silicon substrate to form a silicene layer on the Ag layer; and a carbon-doped silicon layer formation step of forming a carbon-doped silicon layer on the silicene layer.

3. The method for producing a silicon substrate containing a silicene layer according to claim 2, wherein in the Ag layer forming step, the Ag layer is formed to a thickness of 0.3 nm or more by sputtering or vapor deposition.

4. The method for producing a silicon substrate containing a silicene layer according to claim 2, wherein in the silicene layer forming step, the annealing is carried out in an atmosphere at a pressure of 133.3 Pa (1 Torr) or less and a temperature of 1000°C or more.

5. In the carbon-doped silicon layer forming step, epitaxial growth is performed at a growth temperature of 700 to 900°C using a gas obtained by mixing trimethylsilane, monomethylsilane, or monosilane gas with a carbon source as a raw material, and the carbon concentration is 1 x 10 ２０ ~4 x 10 ２１ atoms / cm ３ The method for producing a silicon substrate containing a silicene layer according to any one of claims 2 to 4, characterized in that the carbon-doped silicon layer is formed by:

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